N-(2,2,6,6-四甲基-4-哌啶基-1-氧)-N′-芳酰氨基硫脲EPR波谱的溶剂效应

Solvent Effects on EPR Spectra of Nitroxides of N-(2,2,6,6-Tetramethyl-4-piperidyl-1-oxyl) -N'- (aryl-formyl) thiosemicarbazides

本文研究了五种哌啶类稳定氮氧自由基在九种极性不同的溶剂中EPR谱特性.观察到超精细分裂常数A_N与Kosower Z值、Reichardt E_T值之间存在良好的线性关系.同时还发现=N·O共轭键在外磁场作用下所产生的三组分裂磁能中每两组相邻能级的能量差⊿E、氮原子上的π电子自旋密度P_N~π值与Z、E_T值也有良好的线性关系.以及自由基旋转相关时间τ、高场峰相对高度h_r与溶剂粘度η值之间也呈线性关系.

In this paper the behaviour of five title nitroxides in nine solvents with different polarity has been studied by EPR spectrometry. It was observed that the hyperfine splitting constants A_N of the nitroxides have good linear correlations with some cybotactic solvent parameters such as Kosower constants Z and Reichardt constanta E_T. It was also found that the energy difference of adjacent energy levels AE, as well as the spin-electron density at nitrogen atom P_N~π has good correlation with Z and E constants. Furthermore, the rotational correlation time r, the heights of the upfield EPR lines were found to be linearly correlated with the solvent viscosity η.